SMC Pentax K 28mm f/3.5 on NEX 3, Quick Review

How does this cult classic wide-standard lens perform on modern APS-C Cameras?
This lens has a reputation from various forums as being an excellent performer. Here is a quick review of the lens.

The build quality of this lens is excellent as with all the original K mount lenses, it is also relatively large and heavy because of this. The later M lenses made an effort to miniaturize the existing primes, but they lost the substantial feel of the older Takumars when they did that.

The lens has 8 elements in 7 groups, with a 5 slightly curved bladed diaphragm. The minimum focus distance is good at 0.3 m (1 ft), which is fairly typical for this class of lens, and it is hefty at 261 g (9.2 oz). It uses standard older K filters of 52 mm.

Optical Performance

Please click on the tab you want to view. Only 1 tab may be active at a time. MTF, Distortion, and Lat CA data acquired using Imatest

Comments on the Results

Center sharpness is very good wide open, but does drop off towards the corners. The resolution is relatively good across the frame at all apertures.

Distortion is fairly good for the focal length at -0.87% barrel (numeric average for all apertures).

Lateral CA is very good, better than average for the class of lens.

Pros and Cons

Center performance at all apertures

Entire frame from f/5.6

Build Quality

Large and Heavy

Small Max Aperture

Bottom Line

This lens is a nice solid performer. Relatively low CA and distortion, optically it is well corrected. The corners could be better on digital, but aren’t bad either. I don’t see this lens as special by todays standards, but you can’t really go wrong with it either.

4 Comments

Thanks for the review. I have this lens and a later compact version (Pentax SMC M 28 f3.5) mounted on a NEX-5N. I do not know much about MFT tests, but both lenses are much better than the 18-55 kit lens in sharpness and detail. They surprised me in terms of quality and sharpness!
The M version is much mire compact and it renders excellent color reproduction and contrast. I think both Pentax lenses are above average even at edges especially at F8. Therefore I do not fully agree with your review and I will recommend this land both for street photography and even portraits.

It will certainly be better than the kit lens for Sony, at least my copy of the kit lens that I tested (never posted results with it as I suspect faulty lens), but the Sigma 30 mm f/2.8 or Samsung 30 mm f/2 are significantly sharper in the corners though. For landscapes these Pentax lenses are certainly better than Sony’s own 30 mm f/3.5 macro, being much sharper in the corners.

I made the box green for the Pentax as I definitely recommend the lens if you can get it for a good price, I don’t have any major reservations for it, but obviously this older K version is quite large with an adapter and adds a lot of weight. The M version is obviously much lighter.

I don’t know that they are any better than other similar lenses from other manufacturers though, and some of those aren’t priced with the Pentax used lens premium (i.e. old Pentax lenses are in pretty high demand because of K mount DSLR users).